Silencer



June 23, 1942. R. B. BOURNE SILENCER Filed Dec. 26, 1940 EYS backpressure are both secured.

Patented June 23, 1942 SILENCER Roland B. Bourne, West Hartford, Conn.,assignor to The Maxim Silencer Company, Hartford, Conn, a corporation ofConnecticut Application December 26, 1940, Serial No. 371,603

15 Claims.

This invention relates to silencing devices and specifically to thattype of silencing device in which gas and sound waves are conducted toor from a. chamber by perforated or slotted conduits extending into eachchamber and which may or may not overlap. In plural chamber devices theexhaust conduit from one chamber has been extended from within thatchamber into the adjoining chamber to form th inlet conduit therefor.Such plural chamber silencers, in which the lengths of adjoiningchambers should preferably be different in order to avoid seriesresonance phenomenon, have been much used in the past and give excellentresults.

I have now found that these devices can be even further improved, and atthe same time theirexpense of construction reduced, by providing aplurality of conduits passing through the partition separating. thechambers; both conduits being substantially flush with the partition atone end, and one of them extending into one chamber and the other intothe second chamber.

By this means the length of pipe required for each conduit is reduced toabout one-half, and a material increase in 'thesound attenuatingqualities of the silencer and a decrease in the The invention will nowbe described in connection with the accompanying drawing, in which Fig.i 's a central longitudinal section'through one form of silencerembodying the invention;

Fig. 2 is a section on line 2-2 of Fig.1; and

Figs. 3 to 10 are similar pairs of views showing various modificationsof the invention.

The device of Fig. 1 comprises a generally cylindrical casing [0 havingan inlet header ll, an outlet header l2, and an internal transverseheader l3 which divides the interior of the casing into two compartmentsl4 and I5. These compartments are preferably of unequal length in orderto reduce the passage of unattenuated sound through the device due tolongitudinal resonance within the chambers or conduits. An inlet conduitl6, having lateral escape openings in the form of a longitudinal slot I!or an equivalent row of holes, extends inwardly through the header llinto the interior of the compartment l4 to a point approximately midwaybetween the headers H and I3. The inner end of the conduit I6 is open;so that the incoming pulsating gas is discharged freely from its openend, as well as to a certain extent through the lateral slot ll, intothe compartment H. A discharge conduit I8, having a longitudinal slot19, picks up the gases in the compartment l5 and disopen. end at a pointapproximately in line with the inner end of the conduit l6. From theother of the openings in the header l3 there extends into thecompartment I5 a conduit 22 having lateral escape openings 23 andterminating in an open end approximately in line with the end of theconduit l8.- In the'embodiment shown, the cross-sectional area of eachof the conduits 20 and 22 is half thatof the conduits l5. and It, so

that the combined areas will be equal tothe'area of the latter conduits.

It will be seen that, of all thepulsating gas delivered into thecompartment M, half can pass out directly through the conduit 22, whilethe otherjhalf must .re'verse itself within theicoln partment andfinally. pass into the compartment '15 through the conduit All. The netresult is that the gas surges are :efiectively broken up and smoothedout before passing tothe next compartment, and that the back pressure isreduced to a very low figure. Another benefit results from thisconstruction. .Any tendency towards longitudinal resonance in thecompartment [4 is greatly reduced by the presence of the opening leadingdirectly into the conduit 22 sinc this conduit has its beginning at thesurface of the transverse header I3. It is in this region that pressuremaxima must occur for every frequency for which the compartment l4exhibits any longitudinal resonance tendency. Such a high acous ticpressure is prevented from building up to a point where objectionableresonance phenomena can occur by the free opening into conduit 22. In asimilar manner the conduit 20 acts as an anti-resonating leak for thechamber I5. Strictly speaking the conduits associated with thetransverse header l3 are only a part of the anti-res onance system. Thechamber l5 acts together with the conduit 22 to prevent resonance in thecompartment I4, while the chamber I4 and the conduit 20 act together toprevent resonance in the chamber l5. The conduits 20 and 22 aresufiiciently long and have enough acoustic resistance so that the systemas a whole does not function as a compound resonator. Devices of thistype are particularly adaptable for silencing internal combustionengines having port exhausts, air compressors, and the like.

Figs. 3 and 4 show a similar device, except that the internal transverseheader is positioned midway along the length of the cylindrical casing.This embodiment yields a symmetrical structure and is particularlyadaptable to long discharge or suction lines. Each half of the deviceacts both as a pulse and sound attenuator in itself and also as a.resonance preventor for the other half of the silencer. The structure inthis embodiment being identical with that of Fig. 1 the same numeralshave been used in the two cases.

Fig. 5 shows another embodiment of the invention comprising an inletchamber 24 and an outlet chamber separated by the partition 26. Theinner connection 21 in this case discharges the incoming pulsating gasin the chamber 24.

There are two outlet conduits connecting the chamber 24 with the chamber25; the perforated conduit 28 extending from the header 25 into thechamber 24, and a pipe 28 (here shown as unperforated) extending fromthe header 26 into the chamber 25. In this embodiment the totalcross-sectional area of the two conduits 28, 29 equals that of the inletconduit 21, but the area of the conduit 28 is appreciably larger thanthat of the relatively short conduit 29. This construction isadvantageous where it is desired to improve the high frequencyattenuation of the device. The slotted outlet conduit 30 extends fromthe outlet header to a point in adjacency to the internal transverseheader 26.

Another embodiment of the invention is shown in Figs. '1 and 8. Thisdevice functions as previously described, but differs from the devicesof the preceding figures in that the chambers 3| and 32 have overlappingconduits 33, 34 and 35, 36, respectively. The chambers 3|, 32 are notnecessarily the same size. In this form of device one or more of theconnections can be continued to the opposite header, so that there is nolonger any open end, provided that the area of the laterally openingslot is suillcient to permit the escape of all the gas withoutinjuriously increasing the back pressure.

Fig. 9 shows a device embodying the principles of the invention in whichare employed three chambers 31, 38 and 39, which are preferably all ofdifferent lengths and are formed within the casing by the transverseheaders 40 and 4 I. The two conduits 42 and 43 associated with theheader 40 are shown as spaced along a vertical plane,

while the conduits 44, 45 associated with the header 4| are spaced apartone from the other in a horizontal plane. This arrangement preventsdirect transmission of gas and pulses from one conduit to anotherwithout expanding into the volume of the chamber 38. All conduits arefurnished with lateral escape openings with slots and holes to preventresonance in the conduits themselves and to assist in the breaking up ofthe gas surges.

I claim:

1. A silencer comprising a casing, a partition within the casingdividing it into two chambers, a conduit extending from the partitioninto one of said chambers only, a second conduit extending from thepartition into the second named chamber only, and conduits for theintroduction of gas into one of the chambers and for the exhaust of gasfrom the other of said chambers.

2. A silencer in accordance with claim 1, at

least one of said conduits having lateral escape openings formed alongits length.

3. A silencer comprising a casing, a. partition dividing said casinginto an inlet chamber and an outlet chamber, an inlet conduit extendinginto the inlet chamber, an outlet conduit extending from the interior ofthe outlet chamber, an intermediate conduit extending from a point inthe inlet chamber through but not appreciably beyond the partition andopening into the outlet chamber, a second intermediate conduit extendingfrom the interior of the outlet chamber through but not appreciablybeyond the partition and opening into the inlet chamber.

4. In a silencer having an expansion chamber, two outlet conduits, oneextending into the interior of the chamber and the other extending froma bounding wall of said chamber to a point remote from said boundingwall and outside said chamber.

5. A silencer of the type having two chambers in series separated by apartition, characterized by two separate connecting conduits between thechambers each being inaugurated at and opening through said partition,and extending one into the interior of one of the chambers and the otherinto the interior of the other of said chambers.

6. A silencer in accordance with claim 3 wherein at least one of theinteriorly disposed conduits is furnished with lateral escapeopeningsdisposed along its length.

'7. A silencer in accordance with claim 3 wherein the open ends of theconduits within the chambers terminate at a point substantially midwayalong the length thereof.

8. A silencer comprising an inlet chamber and an outlet chamber, aninlet connection in said inlet chamber and an outlet connection in saidoutlet chamber, said inlet and outlet chambers being separated by apartition having at least two apertures therein, a conduit leading fromthe interior of said inlet chamber to but not beyond one of saidapertures, a conduit inaugurated at the other of said apertures andextending into the interior of said outlet chamber, and an outletconduit extending from the interior of said outlet chamber to saidoutlet connection.

9. A silencer comprising a casing divided into two chambers by apartition, an open ended conduit extending from the interior of one ofsaid chambers through said partition into the other of said chambers butnot extending into it, an open ended conduit extending from the interiorof the second named chamber through the partition and opening but notextending into the first named chamber, the cross-sectional area of oneof said conduits being appreciably larger than that of the other of saidconduits.

10. A silencer comprising a casing, a partition within the casingdividing it into an inlet compartment and an outlet compartment, saidpartition having two apertures therein, an inlet connection in saidcasing communicating with said inlet chamber, an outlet connection insaid casing communicating with said outlet chamber, an inlet conduithaving lateral escape openings disposed along its length extending fromsaid inlet connection into the interior of said inlet chamber andterminating at a point in adjacency to said partition, a conduit havinglateral escape openings along its length extending from a point inadjacency to the inlet end of the inlet chamber to one 01 said aperturesbut not beyond it, a conduit having lateral escape openings disposedalong its length extending from the other of said apertures in saidpartition to a point in adjacency to the outlet end of said outletchamber, and a conduit having lateral escape openings along its lengthextending from a. point in adjacency to said partition to said outletconnection.

11. A silencer comprising a casing, a pair of transverse partitionswithin the casing dividing it into three compartments, a pair ofconduits associated with each of said partitions each conduit extendingfrom the partition in one direction only and the conduits associatedwith each partition extending therefrom in opposite directions intoadjacent compartments.

12. A silencer having an expansion chamber, parallel gas passagesthrough a wall of said chamber, one of said passages being inauguratedwithin the chamber and extending through but not beyond the wall andanother of said gas passages being inaugurated at the wall and extendingan appreciable distance therebeyond.

13. A silencer comprising a casing, a transverse partition within saidcasing dividing it into two chambers, said partition being provided witha pair of apertures, open ended conduits one associated with each ofsaid apertures and extending therefrom into one of the chambers, the twoconduits extending from the partition in opposite directionsrespectively into the two chambers.

14. A silencer comprising casing members forming a plurality ofchambers, a pair of connections in parallel between the chambers oneextending from a point of high acoustic pressure in one chamber to apoint of high acoustic velocity for standing wave systems extendinglongitudinally of the second chamber, and the other extending from apoint of high acoustic pressure in the second chamber to a point of highacoustic velocity for standing wave systems extending longitudinally ofthe first chamber, and means for introducing a pulsating gas into one ofsaid chambers and for conducting the gas from the second chamber.

15. A silencer comprising casing members forming a pair of chambers,conduits in each chamber laterally ofliset one from the other and oneforming an inlet and the other an outlet, and additional connectionsbetween one end wall of each chamber and an intermediate interior pointof the other chamber.

ROLAND B. BOURNE.

